Process of producing three-color photographs



Nov. 22, 1949 A. F. THIEUZARD PROCESS OF PRODUCING THREE-COLOR PHOTOGRAPHS Filea April 26, 1946 COP/ FILM WITH L/ql-IT SINSITNE,

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Patented Nov. 22:, 1949 PROCESS OF PRODUCING THREE-COLOR PHOTOGRAPHS Albert Franois Thieuzard, Paris, France Application April 26, 1946, Serial No. 665,313 In France January 30, 194.6

` found that some of the specific colourings, though they allow to arrive at the wanted result, require careful handling in the preparation of coloured lms, which renders very hazardous an industrial production. For instance, the specified red colouring (S rhodamine) is not firmly fixed by the mordant and the image becomes impaired if washing lasts too long a time. On another hand, the yellow colourings (F yellow, Mikado yellow, Thiazol yellow) penetrate slowly into the gelatine layer, which requires that they remain a long time in contact with this latter.

The object of the present invention is an improvement to the above mentioned process which will considerably facilitate the industrial production of three colour films.

The improved process is similar to the process described in the above-noted patent; it makes use of a lm covered on both faces with a layer of gelatine silver bromide. After exposure 4under two monochrome negatives of the blue and red,

mate process. It has been found that Capri blue (tetramethyl-benzotoluoxazine chlorhydrate) and 5-B Rhoduline blue made by the Farbwerke of Hochst-on-the-Man, Germany (chemical name not known) are suitable for this purpose.

One face of the film bearing the two coloured images is then resensitized by impregnating the gelatine with an alkali bichromate and it is exposed under the monochrome positive of the third colour, yellow. The gelatine becomes insoluble at all places corresponding to the clear parts of the positive and more or less soluble at all places corresponding to the dark parts.

After washing, a yellow colouring is applied on the gelatine; it is more or less absorbed according to the solubility of the gelatine and a yellow image is thus added.

It has been found that none of the presently known yellow dyestuffs is entirely satisfactory. In

se im the film is developed and fixed and two silver images `corresponding to blue and red selection positives are obtained. The silver images are then by a well-known process converted into images which will mordant basic dyes and they are dyed respectively in blue and red by means of basic dyestuffs.

The red image is obtained by means of red colourings derived from triphenylmethane known under the name of fuchsines. These colourings are rmly fixed by the mordant in denite quantity, namely in proportion with the amount of silver forming the image. The excess of colouring is removed by washing and the red image does not grow weak even if the washing is prolonged. The blue image is obtained by means of a basic dye which will not have any subsequent action during the preparation of the image by the bichro- The general formula of these colourings is as follows:

Water, 1 liter Caustic soda, grams or sodium carbonate, 160

grams Naphthylamine 3.6.8. trisulphonic 1 acid, 383

grams Sodium nitrite, '70 grams.

is cooled to 5 C. with ice, and poured out slowly into a cooled vessel containing:

Water, 1 liter Hydrochloric acid, 225 grams The azo derivative precipitates; agitate `so as to obtain a pulp at a temperature of about 10 C. Add slowly this pulp into a solution at a temperature oi 10 to 15 C. containing:

Water, l liter Diacetoacetic tolidide, 190 grams Caustic soda, 40 grams Sodium carbonate, 10 grams The colouring is formed quickly. Neutralize if necessary with hydrochloric acid. The solution may be diluted to a determined Volume or evaporated for getting the dry colouring mixed with sodium chloride.

This new colouring penetrates quickly into the gelatine layer which reduces the time for producing hns and it allows to superimpose the yellow either on the blue or the red image.

The replacement of the colourings previously used by the new ones facilitates the industrial production of three colour films in reducing the time of treatment and in keeping the exact balance of the colours as it corresponds to the basic silver images.

The accompanying drawing indicates the course of the coloring process according to the invention by a briefed iiow diagram.

I claim:

A process for the production of photographic and cinematographic lms in three colors from component monochrome negatives each taken through an appropriate color screen, consisting in exposing the two faces of a lm covered on both faces with a gelatino silver bromide emulsion respectively under two monochrome negatives representing the blue and the red, developing, fixing and converting the silver images into images which will mordant basic dyes, dyeing both Vimages respectively in blue and red by basic dyes,

fthe dyestuff for the med being la fuehsine dye, resensitizing one face of the ilm by bichromate, exposing it under a positive monochrome of the yellow and dyeing with a pinatype dyestuff of the formula in which R is selected from the group consisting of benzene and naphthalene amines bear- -ing'notless than 5 and not more than 6 sulphonic groups.

ALBERT FRANCOIS THIEUZARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

